From: Oleg Nesterov <oleg@redhat.com>
Date: Fri, 26 Jul 2013 17:25:36 +0000 (+0200)
Subject: tracing: Change event_enable/disable_read() to verify i_private != NULL
X-Git-Tag: v3.11-rc5~28^2~15
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bc6f6b08dee5645770efb4b76186ded313f23752;p=pandora-kernel.git

tracing: Change event_enable/disable_read() to verify i_private != NULL

tracing_open_generic_file() is racy, ftrace_event_file can be
already freed by rmdir or trace_remove_event_call().

Change event_enable_read() and event_disable_read() to read and
verify "file = i_private" under event_mutex.

This fixes nothing, but now we can change debugfs_remove("enable")
callers to nullify ->i_private and fix the the problem.

Link: http://lkml.kernel.org/r/20130726172536.GA3612@redhat.com

Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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